Turning our gaze to the celestial vault, in these nights it is possible to observe the planet Mars as bright as it hasn't happened for more than two years. In this beginning of December Mars is close to the Earth and on the 8th it reached its maximum luminosity, being in the opposite direction to the Sun with respect to our planet.
Illuminated by our star, Mars appears red and its brightness is not always the same. Indeed, orbiting around the Sun in just under two years, it approaches and moves away from the Earth. Known since ancient times, the red planet took the name of the god of war Ares, Mars for the Romans, due to its color reminiscent of blood. Observing it with the naked eye as the months go by, it can be seen that its position changes with respect to the constellations, this made it first a god for Man and then a wandering star, a planet. At the first telescopes Mars did not show many details and it had to wait for the nineteenth century, to have telescopes large enough to reveal something of its surface.
In the second half of the 19th century, a race for observations of the red planet was unleashed. Ice caps and apparent continents made Mars a world very similar to Earth. The Italian astronomer Giovanni Schiaparelli, director of the Brera astronomical observatory, observed Mars regularly, drawing up accurate maps of the planet. In his observations he saw that “the vast expanse of the continents is furrowed in every direction by a network of numerous lines or thin strips of dark colour[...]. These lines or streaks are the famous canals of Mars." If Schiaparelli did not express hypotheses on the nature of the Martian canals, others attributed them to a Martian civilization, built to bring water from the poles. The idea that Mars harbored a hypothetical intelligent civilization captured the public imagination. It permeated popular culture so much, that when Orson Welles, in 1938, broadcast the drama "The War of the Worlds" on the radio, a part of the radio listeners actually believed that the Martians were invading the Earth.
The water
But since the beginning of the twentieth century, astronomers had rejected the hypothesis that on Mars there was liquid water on the surface. It was understood that those dark lines seen by Schiaparelli were nothing more than optical illusions, caused by the weak Martian atmosphere and its imposing winds. The true face of Mars could be seen in the 60s and 70s, when the first robotic probes allowed us to discover its cold and desert nature. Covered by a tenuous atmosphere, its average temperature is around 63 degrees below zero, with extremes ranging from -153°C at the poles to 20°C at the equator. There is fine rusty red sand on the surface and winds can blow violently reaching 400 km/h. Extinct volcanoes are present all over the planet, among which the great Mount Olympus stands out, the largest mountain in the Solar System, which exceeds Mount Everest in height by almost three times. Unexpected, however, was the discovery of ancient river beds. Natural channels invisible from Earth, but numerous. There are 200 dry rivers crisscrossing the planet and flowing into what appear to be ancient Martian seas.
The landing
Water is the essential element for life, and the place where life developed on Earth, about 4 billion years ago. The presence of rivers on Mars tells us about a planet that was once the distant twin of the Earth. This discovery ignited the interest of the scientific world and various nations launched various robotic probes on Mars, to study its characteristics and look for signs of the existence of life forms. The relative proximity of the planet allows a probe to reach it in 7 months. The arrival on the planet is the most dangerous part of the journey and if the descent to the planet is foreseen, the landing is something extremely complex and dangerous. Since the Martian atmosphere is thin, it is not enough to open parachutes to slow the arrival of the probe, braking rockets or large airbags must be used to mitigate its fall. Out of 44 missions launched to the red planet, 20 failed. Thanks to the surviving probes, astronomers have begun to understand the nature of Mars and its complex history.
The red planet is a world smaller than Earth, its radius is about half that of Earth. Its gravity is also lower, so much so that a man weighing 100 kg on Earth would weigh just under 38 kg on Mars. The strong temperature variations depend on a combination of factors, on the one hand the distance from the Sun, on the other hand the tenuous atmosphere which retains little heat. Mars in fact has a weak greenhouse effect, which condemns it to be a cold place. But the absence of the magnetic field is the condition that penalizes the planet the most, in fact Mars does not have a shield that protects it from the solar wind. Wind of charged particles that originates from our star, the solar wind continuously erodes the Martian atmosphere and sterilizes the planet's surface.
Like archaeologists, astronomers have reconstructed the history of Mars, which 3.5 billion years ago was very similar to Earth. With its magnetic field extinguished and volcanic activity diminished, the solar wind eroded the atmosphere, dropping temperatures and making the planet a barren and cold place. It has recently been discovered that under the surface near the poles there are seas of salty liquid water, the target of future missions, because they could be cradles for any life forms. These days, the Perseverance rover of the Mars2020 mission is studying the rocks of what was once an ancient Martian lake. Rock samples will be stowed in a special container with the aim of bringing them back to Earth in a future mission, to find out if life has ever appeared on Mars and if anything has managed to survive, to find an initial answer to a fundamental question: does life outside the Earth?
Manuel Floris
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“Science is an art, like music. Nobel-worthy research underway in Cagliari»
Luciano Burderi, Sicilian astrophysicist, teaches at the university and leads a group to discover the most hidden secrets of the cosmos
Before Claudio Ranieri, who became king in 2016 by winning the Premier League, it was he who discovered Leicester, a city in the center of England. «I studied at that University, there was a department that did research on X-rays». It was the nineties. Neutron stars, galaxies, space time. The sacred fire was lit two decades earlier in Luciano Burderi, a 60-year-old from Palermo at the time immersed in classical studies. “But I liked science. I devoured magazines on the subject.' One evening in Cefalù, in a family reunion, an uncle asked for information on black holes. “No one knew what they were. I had read something months before and I replied. I remember the eyes of relatives, shocked. I was thrilled." The road was marked. "At that moment I decided that I preferred astronomy."
Today he is in Cagliari, where he teaches Astrophysics after his degree and PhD in Palermo (and after having worked at the Astronomical Observatory of Rome) where he met the former director of the Astronomical Observatory of the Sardinian capital, as well as president of the 'National Institute of Astrophysics, Niki D'Amico: the man who coordinated the creation of the Sardinia radio telescope of San Basilio. «He offered me the opportunity to come here to strengthen the physics department and its internal astronomy group in view of the creation of the antenna. I accepted the challenge."
And he leads an important Astrophysics school.
"It's a full circle. Astronomy is the most beautiful part of physics because it makes all its instruments play together and at maximum power. Learning also requires long journeys, but then the activity remains. Shape the brain. We must always ask ourselves questions outside the box, observe problems not only on the basis of official solutions but also from other perspectives».
What sequel does such a complicated matter have?
«On average there are about 70 students enrolled in the first year, but most do not complete the three-year cycle. It mostly depends on how you think. The logical deductive ability is a mental habit that is scarce in the school, and it is partly the fault of the teaching class. Especially in scientific disciplines, passion is the driving force behind everything. Often those who arrive in Physics have a very high enthusiasm but come up against the difficulty of having to face an unknown path. This results in a high dropout rate. A serious problem."
So does it make sense to leave the course open?
“Throughout the country, the situation is similar. Those who stay are truly motivated. The faculty has a very good standard, we are involved in international projects. Italian Physics is of a high level, just mention Giorgio Parisi, the very recent Nobel Prize winner. Here is the Sardinia radio telescope, among the five most modern in the world. We scrutinize the radio waves emitted in the cosmic sky. And then the island is fighting an important battle for the great European project of the Eintein telescope».
Why is the Einstein telescope important?
«It could capture the vibrations of space-time, the very structure of the Cosmos, with an accuracy never seen before. Like those caused by two neutron stars that become a black hole: they spread over billions of light years and the Sos Enattos mine could capture them without the influence of surface vibrations».
He mentioned the Nobel. Can Cagliari get there?
"Everything is possible. Genius figures are sprouts that sprout randomly and need to be cultivated. At these levels, reality is perceived differently. It also takes a bit of luck. We teach to be bold».
What bold studies are underway here?
«The largest stars sooner or later collapse under the force of gravity, forming neutron stars a few kilometers large and with gigantic mass. It is as if all of humanity is contained in a sugar cube. These stars spin thousands of times per second and emit light, pulsations, becoming a sort of cosmic clock accurate to the thousandth of a second. Their dual system is the best laboratory for testing Albert Einstein's theory of general relativity. Discovered by D'Amico's research group in Cagliari, it confirmed their theses with a precision never reached before. Any defects can only emerge with a study of decades and we are in it. It's one of the two holy grails of physics."
What's the other?
“General relativity explains that gravity pushes the object crushed by its own weight to become a point. Quantum mechanics instead says that on a very small scale nature does not have well-defined positions, it is not compatible with the existence of perfectly defined points. A clear contrast. So at the smallest levels the General Theory of Relativity has to be replaced by another. We have to check for small discrepancies and from our study of binary systems such discrepancies could emerge that make the rules of the very large match those of the very small. This research field is called Quantum Gravity and could lead to the Nobel Prize».
Since 2020 Cagliari has been working on the Australian Spirit project to launch a satellite with an x-ray detector. Where are we?
«The launch is scheduled for the end of 2023. It is a work that is the result of our beautiful intuition. But Cagliari is truly on the frontier of the most advanced physics research: we, the University of Palermo, the Polytechnic of Milan and Inaf are also working on the international Hermes project conceived by me and my colleagues in collaboration with the Italian Space Agency to launch six nanosatellites the size of a 10 by 30 centimeter box that will study explosions that have occurred in deep space to observe light at different wavelengths. The light that has been traveling for 15 billion years, since the Cosmos was born, would accumulate a delay of a few tens of microseconds along the way. The detection of these delays would be the first experimental confirmation of the effects of quantum gravity. The challenge is to create the technology to measure this data with satellites, which will be launched at the beginning of 2024".
You say that there is no difference between science and art. Is science an art?
«I see an intrinsic beauty in the elegance and logic of the laws of Nature. To do science is to seek beauty. How to make music and paint. It provides you with glasses with which reality is seen and perceived differently. As the musician or the painter use notes and colors to express themselves, mathematics is the tool with which the physicist reveals his feelings and his own vision of the world, anxieties, character. There is a lot of similarity between high-level physics and art».
In 2020 there was talk of the presence, on Venus, of a molecule originating from the decomposition of organic tissues. Have there been any developments?
“The hope that life is present is much reduced. There would be processes capable of producing that molecule, phosphine, and the quantity identified on the planet has perhaps been overestimated».
So I ask you: is there life in space?
“There are a hundred billion galaxies in the universe, each with a hundred billion stars. It is certain that there are planets capable of hosting life. Which surely exists. Not necessarily with terrestrial characteristics. We are not special. The sun is one of the many stars in the Milky Way. What happens to us is not special. Life is the norm in the Cosmos, maybe not everywhere but it's there.'
Why can't you find it?
“For immense distances. It would take 4 years to reach the nearest star, Proxima centauri, going at the speed of light. Perhaps we can focus on the great oceans under the ice crust of Europa or Enceladus, satellites of Jupiter and Saturn. The oldest creatures on Earth are bacteria or the even more primitive procatriotes, which developed around 4.5 billion years ago around underwater hot springs, volcanoes, where light plays no role. Life forms use thermal and chemical energy. Why not think the same could have happened on those two celestial bodies? I'd go explore there."
Andrea Manunza
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The curiosities of the little ones
Six thousand stars light up the night
As dark as the night may appear, the night sky is illuminated by the presence of stars. Moving away from the city and from light sources, getting used to our vision in the dark, we can enjoy the spectacle of the starry sky. Six thousand stars appear in the sky, crossed by a thin trail of light that we call the Milky Way.
Observing these small points of light as the night passes, we understand that they too move from east to west, as happens to the Sun and the Moon. In fact, the whole sky appears to revolve around us. If we look north we realize that there are stars that do not rise and set. In particular, we are struck by the presence of a large figure, which recalls the shape of a spoon and which was called the Big Dipper. This massive asterism rotates counterclockwise around a point, there is a star called Polaris. The Polar star is not particularly bright, but it is located on what we can call "the tip of the Earth top".
In fact, our planet rotates on itself as if it were a top, therefore it moves around the earth's axis. By pure chance, the earth's axis points north towards Polaris, with such great precision that thanks to Polaris we can orient ourselves at night and not lose our way. Not only the Big Dipper, but by uniting the stars, we can represent many figures in the sky, which we call constellations.
How many stars are there in the sky?
There are many stars, but we can observe about 6000. The 400 brightest have a name, some are well known such as the North Star and Sirius.
How far away are the stars?
The stars are very far away. If we traveled to our star, with the spaceship that brought men to the Moon, we will arrive on the Sun in about 3 years. If we boarded the same spacecraft and aimed at the closest star, which is called Proxima Centauri, we would travel in space for more than 70,000 years (3.75 light years).
What color are the stars?
The stars have different colors, Blue, Yellow, Red and White. Unfortunately we can only see the color of the brightest stars, many are too faint to show us their true color and appear white.
The color of a star tells us about its temperature. The coldest stars are the Red ones, then there are the slightly hotter Yellow stars, while those with the warmest temperatures are the Blue and White ones.
How far away is the sun?
The closest star is the Sun, it is 150 million km away from us. If you zoomed out across the solar system so that the sun was the size of a soccer ball, the earth would be 25 meters away.
How come the stars fall?
Shooting stars are not stars, but small pieces of ice and dust that fall to Earth. Our planet is covered in a thin shell of gas we call air. When the ice and dust pass through the air, they burn and leave a trail of light that we see in the night sky.
What is the brightest star?
The brightest star is called Sirius and can be seen in the winter sky. After her is the star Canopus, invisible from Sardinia. In third place is the star Arcturus, clearly visible in spring and summer.